Molten zinc attacks metals such as steel and the like and easily penetrates into small holes or gaps in the micrometer range because of its low surface tension and viscosity. Some protecting methods are proposed or are in use for improving the resistance to molten zinc, as for example, specially developed steels as disclosed in Laid Open Japanese Patent Application No. S56-112117 and applying a thermally sprayed WC-Co coating as disclosed in Japan Patent Application Laid Open No. 111-225761. However, these approaches are not sufficiently resistant to molten zinc attack.
Molten zinc resistant steels are basically iron base alloys and do not have enough resistance to molten zinc attack. The cost of those alloys are much higher than normal structural steels. Coatings such as self fluxing alloys and WC-Co are used as thermally sprayed coatings to protect substrates from attack by molten zinc, but sufficient resistance has not been achieved due to the permeation of molten zinc through interconnected porosity and selective attack on the metal binders.
Some sealants that provide protection for rolls used in zinc pots on galvanizing lines, have a tendency to accumulate oxides, dross and the like on the surface of such rolls during operation. The buildup of these oxides, dross and the like could mark steel strip passing over the rolls thus resulting in poor quality steel products.
It is an object of the present invention to provide a boron nitride and silicate sealant for articles, such as rolls that are intended to come into contact with or be immersed in a molten metal, to provide resistance to molten metal attack and minimize buildup of oxides, dross and the like on the surface of such articles. As used herein dross means an intermetallic alloy or compound of, but not limited to aluminum, zinc, iron and combinations thereof.
Another object of the present invention is to provide a boron nitride-silicate sealant that is easy to apply and cost effective to produce.